Permanent magnets based on compositions containing iron, neodymium and/or praseodymium, and boron are known and in commercial usage. Such permanent magnets contain as an essential magnetic phase grains of tetragonal crystals in which the proportions of, for example, iron, neodymium and boron are exemplified by the empirical formula Nd.sub.2 Fe.sub.14 B. These magnet compositions and methods for making them are described by Croat in U.S. Pat. No. 4,802,931 issued Feb. 7, 1989. The grains of the magnetic phase are surrounded by a second phase that is typically rare earth-rich, as an example neodymium-rich, as compared with the essential magnetic phase. It is known that magnets based on such compositions may be prepared by rapidly solidifying (such as by melt spinning) a melt of the composition to produce fine grained, magnetically isotropic platelets of ribbon-like fragments. Magnets may be formed from these isotropic particles by practices which are known Although the magnets formed from these isotropic ribbons are satisfactory for many applications, there is always a desire to improve the magnetic properties of these isotropic, melt-spun ribbons.
Lee, U.S. Pat. No. 4,782,367, issued Dec. 20, 1988, went on to demonstrate that the melt-spun isotropic powder can be suitably hot pressed and hot worked by plastically deforming to form high strength anisotropic permanent magnets. Such magnets have excellent magnetic properties. Typically, the hot working of these anisotropic magnetic bodies is accomplished at a temperature of about 1500.degree. F. or higher.
It would be desirable to provide a method for hot working these anisotropic magnetic bodies at lower temperatures since any reduction in the temperature will significantly enhance the life of the machinery, particularly the punches and dies, employed during the hot working, as well as also generally make the processing of such magnets simpler In addition, another advantage associated with hot working of these magnets at lower temperatures is that grain growth is decreased within the alloy during the hot pressing operation, resulting in a more homogeneous composition characterized by uniform magnetic properties throughout.
Therefore, although these prior art methods have worked satisfactorily to produce anisotropic magnetic bodies, it would be desirable to provide a means for hot working these bodies at reduced temperatures without any loss in magnetic properties In addition, as previously mentioned, it would be desirable if such a means concurrently enhanced the magnetic properties of the melt-spun material also.